The invention concerns a filter system, in particular for use as an air filter in an internal combustion engine, as well as a filter element for installation in such a filter system.
WO 2009/047196 A1 discloses a filter system for internal combustion engines in which a secondary element is provided which is arranged in an inner space of the filter element of the filter system. The secondary element has the task of keeping closed the outlet of the filter system when exchanging the filter element so that no dirt can penetrate into this area while the filter element is cleaned or replaced. In operation of the filter system the purified air flows through the secondary element which comprises a nonwoven layer on a support structure. The secondary element is connected by means of a screw thread to the outlet socket of the outlet and, at the same time, is sealed by an O-ring in this area.
In principle, it is provided to exchange the filter elements of air filters after a certain operating time. Depending on the amount of dust that is collected, the service life of a filter element can be a few days (construction machinery) up to several months. In this context, the secondary element, arranged on the clean air side, remains usually within the filter system. However, when the secondary element is also strongly loaded with dirt, it must also be exchanged because otherwise the air throughput would be reduced too much. In this context, the reliable sealing action of filter element and secondary element in a housing ensuring safe operation is particularly important in order to protect the intake manifold of an internal combustion engine arranged downstream of the filter system from penetration of dirt.
The object of the invention is to provide a filter system in which a service-friendly attachment and detachment of a secondary element from its fastening means in the housing is enabled.
A further object of the invention is to provide a filter element and a secondary element for installation in such a filter system.